This invention relates to the switching control of relatively high voltage, DC or low frequency, signals with relatively low voltage, high frequency, pulses. This invention also relates to the use of such control to provide a stable frequency power supply for facsimile transceivers and the like.
In many applications, it is desirable to provide switching control of DC or low frequency sources of relatively high voltages. This control may be provided by digital logic circuitry. However, suitable precautions should be taken to isolate the low voltage logic circuitry from the high voltage source, and such precautions can be rather costly.
One particularly important application of the foregoing is facsimile transceivers wherein it is desirable to provide a stable frequency power supply for the synchronous motor which drives the rotatably mounted, document/copy carrying drum of the transceiver. As shown in U.S. Pat. No. 3,582,550 - Latanzi, the output from a stable frequency oscillator is applied to a frequency generator comprising a series of logic elements which produces a periodic pulse which is applied through gate means to control the synchronous motor. Thus, the Latanzi patent discloses a circuit wherein logic elements are utilized to achieve a relatively high voltage, stable frequency power supply. It does not however disclose any means by which isolation may be achieved between the logic circuitry and a high voltage power supply.